Method and apparatus for scale breaking and edging hot metal slabs



Nov. 3, 1936. I WERSEN 2,059,460 METHOD AN]? APPARATUS FOR SCALE BREAKING AND EDGING fiOT METAL SLABS .Filed Sept. 20, 1952 e Sheets-Sheet 2 &

INVENTOR NOV. 3, 1936. [VERSEN A 2,059,460

I METHOD AND APPARATUS FQR SCALE BREAKING AND EDGING HOT METAL SLABS a 4 Filed Sept. 20,1932 9 Sheets-Sheet s INVENTOR QM m fi ad? L. IVERSEN 2,059,460

METHOD AND APPARATUS FOR .SC ALE BREAKING AND EDGING HOT METAL SLABS Nov. 3, 1936.

Filed Sept. 20, 19 32 9 Sheets-Sheet 4 INVENTOR W,

-NOV. 3, 1936. [V 2,059,460

METHOD AND APPARATUS FOR SCALE BREAKING AND EDGING HOT METAL SLABS Filed Sept. 20, 1932 9 Sheets-Shee 5 INVENTOR L. IVERSEN 2,059,460

METHOD AND APPARATUS FOR SCALE BREAKING AND EDGING HOT METAL SLABS Nov. 3, 1936.

Filed Sept. 20, 1932 9 Sheets-Sheet 6 I INVENTOR L. IVERSEN Nov. 3, 1936.

METHOD AND APPARATUS FOR SCALE BREAKING AND EDGING HOT METAL SLABS Filed Sept. 20 1932 9 Sheets-Sheet 7 INVENTOR L. IVERSEN Nov. 3, 1936.

METHOD AND APPARATUS FOR SCALE BREAKING AND EDGING HOT METAL SLABS Filed Sept. 20, 1932 9 Sheets-Sheet 8 R O T N E V m IVERS'EN Nov. 3, 1936.

METHOD AND APPARATUS FOR SCALE BREAKING AND EDGING HOT METAL SLABS 9 Sheets-Sheet 9 Filed Sept. 20, 1932 lk r llllllllllll ll erally, it is particularly atented Nov. 3, I, 1936 UNITED STATES METHOD AND APP BREAKING AND SLABS Lorenz Iversen,

ARATUS FUR SCALE EDGIN G HUT IMETAL Pittsburgh, Pa., assignor to Mesta Machine Company, Homestead, Pa, a corporation of Pennsylvania Application September 20, 1932, Serial No. 633,960

11 Claims.

The present invention art of metal working, and generally that phase of the art dealing with the rolling of metals, and more particularly to a method and apparatus for the breaking or loosening and removal of scale or oxide from metal bodies which are to be subjected to further rolling.

The invention is applicable more particularly to the treating of slabs and effects not only a removal of scale or oxide of the character referred to, but also a sizing and truing of the slab edgespreparatory to further rolling. While the invention is useful in connection with mills genapplicable to mills of the type commonly known as strip mills which are usually of the continuous type embracing a plurality of mill stands arranged in tandem and adapted for effecting succcessive reductions in thickness of the metal as it passes progressively from. one stand to the next. It will be obvious, however, that the invention is useful with any type of mill working on a hot metal piece of such shape and dimensions as to be suitable for treatment in accordance with my invention.

It is well known to'the art that one of the prerequisites of the succcessful rolling of what is commonly known as strip, is the thoroughremoval, before rolling, of the scale or oxide that forms on heated metal upon exposure to an oxidizing atmosphere. This scale may be of varying thickness, and forms either in the open air or in the atmosphere of the ordinary heating furnace, so that the method applies equally Well to slabs, for example, that are received hot from previous rolling in a primary or slabbing mill, or to' slabs that have been reheated in an ordinary heating furnace. It consists usually of a more or less adherent layer or film of oxide which, if rolled into the metal, makes it impossible to produce a satisfactory surface on the resulting product. Inasmuch as surface specifications are becoming more and more rigid, the

problem of scale removal assumes even greater importance today than previously.

One characteristic of scale of the general character referred to, and a property which is taken advantage of in accordance with the present invention, is that it is comparatively brittle as contrasted with the plastic consistency of the hot metal on which the scale forms, at the rolling temperature.

Several methods have heretofore been-practiced for the purpose of breaking or loosening and more or less efiectively removing the brittle skin of scale heretofore referred to, One of the relates broadly to the most common and successful methods has com prised rolling the edges of the slab between opposing rolls known as edging rolls which serve to effect a reduction in the width of the plastic slab. The layer of scale being brittle, is not compressed with the slab, but shatters more or less at the points where the rolls engage the metal, metal.

These edging rolls may be either on vertical axes, in which case the slab engages them in a horizontal plane, or the slab may be edged in a vertical plane between rolls turning on horizontal axes. In either case, the portion of the slab surface where the scale is effectively loosened is usually confined to comparatively small areas nearest to the points of roll engagement. In the case therefore of extremely wide slabs, the scale in the middle of the slab is not eifectively loosened, because the work done by the edging rolls is local and does not penetrate to the middle of the slab. This has constituted one definite limitation on the emciency of scale removal by edging rolls.

A second limitation has been reason of the fact that and thus breaks loose from the parent occasioned by the rolls work on only a very short length of the slab at a time measured in the direction of slab travel. These two limitations, thoughrecognized, have heretofore not been effectively overcome.

Another method of scale breaking which has been more or less commonly used, comprises passing the slab in a horizontal plane through a stand of rolls adapted to take a light pass which, while not reducing the slab much in thickness, works the metal sumciently to loosen the scale. This method, while fairly satisfactory, sometimes fails to remove patches of scale which are particularly adherent. As to such patches, the tendency is to imbed them more deeply into the parent metal. In addition to this, it is diilicult to adjust the mill screws for the exact draft which is most effective for scale breaking, variations in slab thickness requiring compensating adjust- 1 ment of the screws if the best results are to be obtained. It is thus apparent that the rolling 'process of scale removal has not been entirely satisfactory.

In accordance with the present invention,

there is utilized a method of scale breaking The present invention briefly, comprises sub- L jecting the edges of the slab to simultaneous sustained pressure, preferably in a horizontal squeezer or press, sufficient to reduce the width an appreciable amount throughout a very appreciable length of the slab. If the slab sizes are such as to permit, I preferably subject the entire length to pressure of the character referred to in a single operation. If this is impracticable on account of the extreme length of the slab being operated upon, the leading end of the slab is entered between the jaws of the press or squeezer to approximately the full length of such jaws, and the pressure exerted on such portion as described; The slab is then released, again advanced, by an amount approximately equal to the length of the jaws, and subjected to a second stroke effective for reducing the width of the slab exactly the same amount as the first operation. This may be repeated as often as is necessary until the entire length of the slab has been reduced equally in width from one end to theother, the edges equally trued and sized, and the scale effectively loosened.

The loosening occasioned by the squeezing process is the result of shattering the brittle coat of scale over the entire width of the slab due to the fact that the plastic metal under the brittle skin will fiow freely and evenly under the pressure exerted, while the scale, on account of its brittleness, shears loose from the underlying metal and shatters into small pieces which drop readily from the under surface ofthe slab and may be easily blown or the upper surface thereof by the use, for example, of a suitable jet of steam, water or the like.

In certain cases provision is also made for turning the slab over, the better to remove the scale with equal effectiveness from both the top and bottom surfaces thereof.

In addition to the scale breaking effect, the method of squeezing the slab edgewise possesses the further important advantage, briefly referred to, of making the edges more truly parallel, since it is possible to control or change the width of the slab within certain limits by the squeezing operation so that the width of the resulting strip may be varied somewhat as rolled from the same width of slab. For this reason, the. method is particularly useful following what is known as a spreading mill, which comprises a mill stand of a width suitable for accommodating the long di- 'mension of the slab. One or more passes through the spreading stand, elongates the short dimension of the slab due to the cross rolling operation. The slab is then turned from the direction of rolling, and subjected to a squeezing operation. The resulting slab is wider than the original slab by the amount of elongation in the spreading stand, and the uneven or irregular edges that emerge from the, spreading stand are {trued and corrected by the squeezer.

'In the accompanying drawings I have shown 'for' purposes of illustration only, certain preferred embodiments of the present invention, the

otherwise removed from figures of the drawings in many cases being largely diagrammatic for the purpose of giving a clearer understanding of the present invention without needless complication as to the par- Figure 1 of another embodiment of my invenerably made entirely by one tion;

Figure 3 is a plan view of a scale breaking squeezer with the roller tables serving it and a transfer and turn over for turning the slabs to effect a more thorough removal of the scale, and constitutes a showing in greater detail of a portion of the system illustrated in Figure 1;

Figure 4 is a view partly in plan and partly in section of the squeezer illustrated in Figure 3;

Figure 5 is a detail sectional view through the squeezer of Figure 4 along the line V-V of Figure 4;

Figure 6 is a detail sectional view of the slab turn over mechanism;

Figure '7 is a view, generally similar to Figure 3, illustrating in greater detail a portion of the system diagrammatically shown in Figure 2;

Figure 8 is a view partly in section and partly in elevation in a plane parallelTto the direction of slab travel, of the squeezer illustrated in Figure 7;

Figure 9 is a detail sectional view on the line IX-I X of Figure 8;

Figure 10 is a detail sectional view along the line X-X of Figure 8;

Figure 11 is a view partly in section, and partly broken away, and generally along the line XI-XI of Figure 10;

Figure 12 is a plan view of the electro-hydraulic drive for the hydraulic squeezer shown more particularly in Figures 8 to 11; and

Figure 13 is a view partly in section and partly in side elevation of the drive shown in Figure 12.

Referring first to Figures 1 and 3, a slab 2 produced in any desired manner and having a skin of scale thereon which it is desired to remove, is conducted to a suitable squeezer 3 by conveying means such as a roller table 4. The squeezer comprises opposed jaws 5 and 6-each of which is preferably movable in opposite directions as indicated by the arrows I. The slab having been suitably spotted between'the opposed jaws 5 and 6 is subjected to a scale breaking stroke prefrelatively to the other jaw, although this is not essential. .It is then conducted away from the squeezer by a second conveying means such as a roller table 8, delivering to a transfer mechanism 9 from which it is moved transversely to turn over fingers I0 effective for engaging it and turning it over'to accomplish a more thorough removal of the scale loosened by the squeezing operation.

In Figures 4 and 5 the squeezer is shown in greater detail. As herein illustrated it comprises in effect a horizontal crank press having a frame H in which is journaled a double crankshaft l2.

Carried by each of the throws or cranks I4 of the shaft I2 is a pitman IS the ends of which cooperate with? ram l6 fitted with the squeezing jaw 5. The opposing jaw 6 is carried by a ram 11 which is moved by two screws l8 rotatable in stationary nuts I!) which are effective for advancing or retracting the jaw 6 to accommodate slabs of different widths. The screws may be provided with a suitable drive comprising a pair of worm gears 20 with which mesh worms 2| connected by couplings '22 to a common shaft 23. Secured to the shaft 23 is a helical gear 24 meshing with a helical pinion 25 driven through a suitable shaft and coupling 26 from an electric motor or the like, not shown.

The main drive for the squeezer comprises a gear 2'! loosely journaled on the shaft i 2 and meshing with a pinion 28 which may be formed The clutch may be, of any well known type adapted to start the crank shaft from a position on or near its rear dead center, and remain in engagement until the crank has moved through an angular distance of 360 effective for retuming it to its starting position, at which time the clutch is disengaged. An auxiliary motor 34 may be utilized for engaging the clutch after it has automatically disengaged by an angular travel of the extent referred to. This type of clutch mechanism-is well understood in the art and constitutes no essential part of the present invention.

It will be understood that, each time it is desired to perform a squeezing operation on a slab which has been properly spotted between the jaws 5 and 6-of the squeezer, the auxiliary motor 34 is energized in any desired manner to effect a single rotation of the crank shaft l2.

Before a slab enters the squeezer, the jaw 6 is adjusted by means of the screws l8 to get the desired width slab after the completion of the scale breaking stroke. Since the clutch mechanism is arranged to stop the crank motion on rear dead center, which is the position illustrated in Figures 4 and 5, the slab may be easily entered between the jaws on suitable rollers 35 and correctly spotted as nearly as possible in the center of the squeezer.

The jaws 5 and 6 are illustrated as provided with lugs 31 having inclined upper surfacesSli.

- These lugs project downwardly between the rollers 35 as clearly apparent from the drawings in such manner that as the squeezer jaws come together during the, scale breaking stroke, the lugs tend to lift the slab from the rollers so that as the scale breaks under the squeezer stroke, it may be shed freely from the bottom of the slab. As the slab is released during the return stroke of the squeezer, it will again ride on the table rollers 35 and can thus be moved from the squeezer to conveyor 8 effective for delivering it to the transfer mechanism 9 and the turn over fingers in.

In Figure 6 this turn over mechanism is illustrated in cooperative relation to the transfer mechanism. From the illustrated embodiment, it will be apparent that the transfer mechanism comprises endless chains 39 adapted to move slabs 2 transversely from the roller table 8 onto suitable skids an and into position over the fingers l0.

Thesefingers are arranged in groups, one group being carried by a shaft 4! and the other group by a similar shaft 42. Projecting respectively fromthese shafts are levers 43 and 24 adapted to be oscillated by connecting rods t5 and t5 through the medium of crankarms l1 and 48. These cranks are so arranged on a common shaft 49 that the fingers ID of one group raise the slab to approximately a vertical position in which position it is received by the fingers of the other group which allow it to drop to the skid bed by means of whichit is conveyed into transfer relationship to a roller table 50, which may deliver to a suitable mill such as a tandem mill 5i (Figure 1). The turn over mechanism is a typical turn over device of the type commonly utilized for turning plates, its purpose in the present system' being to turn the slabs subsequent to a squeezing operation so that any scale adhering to the top surface of the slab, having reference to the position it occupied during the squeezing opera tion, is loosened and falls ofi as the slab is turned over and dropped onto the skids. v

It will be apparentthat the cycle just described is effective not only for thoroughly removing the r film of scale uniformly throughout the entire width of the slab, but for truing the edges of the slab and controlling its width for delivery to a subsequent mill. 7

In Figures 2 and 7 of the drawings there is illustrated another embodiment of the invention wherein a squeezer 3' working generally on the principle just described is arranged behind a cross rolling mill stand 52, constituting a spreading stand for a slab 2'. The slab after emerging'from the spreading stand is turned by a suitable turn table 53 and is conveyed to the squeezer 3' by conveying means such as a roller table 54.

The squeezer illustrated diagrammatically in Figures 2 and 7 of the drawings is shown in detail in Figures 8 to 11. As apparent from thesefigures, it comprises a massive frame 55 constituting a mounting for hydraulic cylinders 56 and 51. These cylinders are provided, respectively, with plungers 58 and 59 which are adapted to move in the cylinders under hydraulic pressure, and are guided in bearings 60. The squeezing ram GI and jaw 62 of the squeezer 3 are carried'on the ends of these plungers and movable thereby as the plungers are operated. The opposite jaw 63 is similarly carried by a ram 54 provided with a screw adjustment 65 of the general nature previously described for opening the jaws to accommodate slabs of different widths. This squeezer .or press performs the same function as the crank press previously described and, in addition, being located behind the spreading stand, serves to true up and make parallel those uneven or irregular edges that emerge from the spreading stand after has its own hydraulic line I3 and M respectively,

for connecting the pump cylinders to the squeezer cylinders 56 and 51. Since the two plungers 68 and 69'move as one under the influence of the double crank 12, an equal displacement of fluid enters the cylinders 56 and 51 so that their respective plungers travel the same amount as the cranks move the plungers 68 and 59 on the forward stroke.

On the return stroke, a suitable pull back plunger l6 returns the plungers 5t and 55 by means of pull back rods ill and it which are suitably secured at one end to the ram 6i and at the opposite end to a cross-head 19. The pull back cylinder "I6 is constantly open to pressure from a suitable hydraulic accumulator or the like (not shown) so that the forward movement of the squeezer plungers is made against this pressure, the fluid being returned to the accumulator on the forward or working stroke of the squeezer. On the backward stroke, horse-shoe shaped stops 80 limit the return stroke. When the pull back cylinder pulls the pull back rod collars 8| against these stops, fluid may enter the main cylinders 56 and 51 through suitable check valves 82. The under side of these check valves is constantly subjected to pressure sufficient to fill the system, but not sufficient to advance the ram 6| against the effort of the pull back cylinder 16. l

The single stroke pump shown in Figures 12 and 13 may be provided with a drive generally similar to that shown in Figures 4 and forthe mechanical squeezer, except that in this case. there is no need of using a clutch of the character referred to, it being possible to start and stop the motor for each stroke of the crank.

By reason of the structure described, the hydraulic press is capable of making a short power stroke of a length dependent upon the displacement of the plungers 68 and 69, and the relative areas of these plungers with respect to the squeezer plungers 58 and 58. However, by admit-' ting fluid from the accumulator through suitable valves to the cylinders 56 and 51, by suitably raising oropening the check valves 82, the ram may be advanced as far as required, the power stroke beginning from the point at which the cranks start moving forwardly from dead center position.

The opening of the valves 82 may be accomplished in any desired manner as, for example, by utilizing levers 83 (Figure 9) cooperating with a thruster 84. By reason of the fact that the jaw 63 may be adjusted by the screw mechanism 65, and the jaw mechanism 62 by admitting fluid in the manner referred to, there is provided an adjustment for width of slabs on both sides of the squeezer. This makes it possible to work with the slab in the center of the squeezer directly under plungers 85 carrying a hold down plate 86 to prevent possible buckling of the wide slabs as the pressure is exerted on the edges.

It will be understood that generally the hydraulic squeezer effectively accomplishes the same general objects before referred to, namely, the breaking or loosening and removal of the scale from the slab concomitantly with the sizing and truing of the edges preparatory to further rolling. As in the case of the mechanical squeezer, slabs squeezed in the hydraulic squeezer may be conveyed in the general manner described to a suitable transfer and turn over mechanism before delivery to a mill for a further rolling operation.

From the foregoing description, it will be understood by those skilled in the art that the provision of a squeezer effective uniformly or substantially uniformly throughout an appreciable length of a slab is distinctly advantageous not only from the standpoint of scale removal, but from the standpoint of accuracy of slab size obtainable thereby. The advantages of scale re-' moval are accomplished without the'limitations characteristic of an edge rolling mill, and without the objectionable scale rolling in characteristic of a light draft mill as heretofore utilized for scale breaking purposes.

Certain features of my invention, particularly those concerned with the slab turning mechanism, are described and claimed in my copending application Serial No.

descaled, a pair. of cooperating elongated jaws extending along opposite sides of the conveyor, the jaws being relatively reciprocable toward and away from one another, adjusting means for at least one jaw whereby such reciprocating movement will be automatically terminated upon successive reciprocating movements at a predetermined adjusted minimum spacing of the jaws so as to .insure that successive slabs will be uniformly sized, and power means for moving at least one jaw so as to effect such reciprocating movement.

2. Apparatus for breaking scale from the faces of hot metal slabs comprising a conveyor for advancing and supporting successive slabs to be descaled, a pair of cooperating elongated jaws extending along opposite sides of the conveyor and adapted simultaneously to engage all points along the opposite edges of the slab being treated, the jaws being relatively reciprocable toward and away from one another, means for effecting a predetermined minimum spacing of the jaws upon such reciprocating movement whereby to insure that successive slabs will be uniformly and properly descaled, and power means for moving at least one jaw so as to effect such reciprocal movement.

3. Apparatus for breaking scale from the faces of hot metal slabs comprising a conveyor for advancing and supporting successive slabs to be descaled, a pair of cooperating elongated jaws extending along opposite sides of the conveyor and having continuous faces, the jaws being relatively reciprocable toward and away from one another, means for effecting a predetermined minimum spacing of the jaws upon such reciprocating movement whereby to insure that successive slabs will be uniformly 'and properly descaled, and power means for moving at least one jaw so as to effect such reciprocal movement.

4. Apparatus for breaking scale from the faces of hot metal slabs comprising a conveyor for advancing and supporting successive slabs to be descaled, a pair of cooperating elongated jaws- .a plane for a sufficient distance to engage the opposite edges of a slab under treatment along its entire length, the jaws being relatively reciprocable toward and away from one another, means for effecting a predetermined minimum spacing of the jaws upon such reciprocating movement whereby to insure that successive slabs will be uniformly and properly descaled, and power means for moving at least one jaw so as to effect such reciprocal movement.

5. Apparatus for breaking scale from the faces of hot metal slabs comprising a conveyor for advancing and supporting successive slabs to be descaled, a relatively fixed jaw extending along one side of the conveyor, a movable jaw extending along the other side of the conveyor, the jaws extending along ing buckling of the being adapted to engage opposite edges of a slab advanced to them by the conveyor, means for reciprocating the movable jaws and adjusting means for one of the jaws for effecting a predetermined minimum spacing thereof upon such reciprocating movement whereby to insure that successive slabs will be uniformly treated and adequately descaled,

6. Apparatus for breaking scale from the faces of hot metal slabs comprising a conveyor for advancing and supporting successive slabs to be descaled, a pair of cooperating. elongated jaws opposite sides of the conveyor, the jaws being relatively reciprocabletoward and away from one another, means for effecting a predetermined minimum upon such reciprocating movement whereby to insure that successive slabs will be uniformly and properly descaled, power means for moving at least one jaw so as to effect such reciprocal movement, and hold-down means above the plane of the conveyor and effective for preventslab during the descaling operation.

7. Apparatus for breaking. scale from the faces of hot metal slabs comprising a conveyor for advancing and supporting successive slabs to be descaled, a pair of cooperating elongated jaws extending along opposite sides of the conveyor, the jaws being relatively reciprocable toward and away from one another, means for eflecting a predetermined minimum spacing of the jaws upon such reciprocating movement whereby to insure that successive slabs will be uniformly and properly descaled, power means for moving at least one jaw so as to effect such reciprocal movement, and hold-down means above the plane of the conveyor and efiective for preventing buckling of ,the slab during the descaling operation, the hold-down means engaging the slab under treatment over a major portion of its length.

8. Apparatus for breaking scale from the faces of hot metal slabs comprising a conveyor for advancing andsupporting successive slabs to be descaled, a pair of cooperating elongated jaws exspacing of the jaws tending along opposite sides of the conveyor, the jaws being relatively reciprocable toward and away from one another, means for eifecting a predetermined minimum spacing of the jaws upon movement whereby to insure such reciprocating that successive slabs will be uniformly and properly descaled, power means for moving at least rowing the slab, the pressure being exerted in sufficient amount to cause a. movement of the metal over the entire width of the slab so as to loosen the adherent scale over its entire width.

10. A method of descaling wide slabs which includes the steps of applying pressure to the edges of the slab throughout substantially the'entire length thereof at one time, thereby slightly narrowing the slab, the pressure being exerted in sufficient amount to cause a movement of the metal over the entire width of the slab so as to loosen the adherent scale over its entire width, and simultaneously restraining the slab, over a major portion of its length, against bulging.

11. A method of descaling wide slabs in an apparatus having a conveyor and cooperating squeezing jaws, which includes the steps consisting in operating the conveyor in such manner as to advance successive slabs to a position between the jaws, checking the forward movement of each slab at such position and moving the jaws with the successive slabs therebetween to a predetermined minimum spacing sufliciently less than the original width of the slabs to cause a movement of the metal over the entire width of the slabs and thereby loosening the adherent scale over their entire width.

LORENZ IVERSEN. 

